The invention relates to a method of encoding a picture signal to obtain an encoded picture signal, comprising the steps of:
receiving said picture signal,
determining motion vectors relating to motion in a picture of said picture signal,
obtaining a selection signal to select one operation mode out of a plurality of possible operation modes on said picture signal depending on said selection signal to obtain a picture signal to be encoded,
digitally encoding said selection signal and said motion vectors to obtain an assisting signal to inform a decoder which one of said plurality of operation modes has been selected and about said motion vectors, and
encoding said picture signal to be encoded and said assisting signal to obtain said encoded picture signal.
The invention also relates to an apparatus for encoding a picture signal to obtain an encoded picture signal, comprising:
means for receiving said picture signal,
means coupled to said receiving means for determining motion vectors relating to motion in a picture of said picture signal,
means for obtaining a selection signal,
means coupled to said selection signal obtaining means for selecting one operation mode out of a plurality of possible operation modes on said picture signal depending on said selection signal to obtain a picture signal to be encoded,
means coupled to said selection signal obtaining means and said motion vector determining means for digitally encoding said selection signal and said motion vectors to obtain an assisting signal to inform a decoder which one of said plurality of operation modes has been selected and about said motion vectors, and
means coupled to said selecting means and said digitally encoding means for encoding said picture signal to be encoded and said assisting signal to obtain said encoded picture signal.
The invention further relates to an apparatus for decoding a picture signal to obtain a decoded picture signal, comprising:
means coupled to receive said picture signal for decoding said picture signal to obtain a picture signal to be processed and an assisting signal including a selection signal and a motion vector information signal,
means coupled to said decoding means to receive said selection signal and said motion vector information signal for selecting one operation mode out of a plurality of possible operation modes on said picture signal to be processed depending on said selection signal, at least one of said plurality of possible operation modes including a motion compensated interpolation using said motion vector information signal.
Such a high-definition television system is described in the Proceedings of the Second International Workshop on Signal Processing of HDTV, 29 Feb. to 3 Mar. 1988, L'Aguila, Italy, in a paper of M. R. Haghiri et al., entitled "Motion Compensated Interpolation applied to HD-MAC pictures encoding and decoding." For television the introduction of high-definition television (HDTV) for home use is described. Based on what is commonly referred to as the MAC-system (Multiplexed Analog Components) with its limited bandwidth a compatible high-definition system (HD-MAC) is described. In the description it is assumed that there must be a balance between the best HD-MAC picture available for specific receivers and the capability of preserving an acceptable quality for existing MAC-receivers. To that end it is proposed to use in the encoder circuit and the complementary, i.e. inversely operating, decoder circuit three picture signal channels having a shortest, a medium and a longest picture signal refresh period, the shortest period being equal to 20 ms. Depending on a motion estimation result one of the three channels is utilized locally in the picture. When the motion exceeds 3 picture elements per picture period (20 ms), the channel having the shortest period is used. For motion between 3 and 0.5 picture elements per picture period the channel having the medium period is used and motion vectors are transmitted to allow for a motion compensated interpolation in a decoder. For motion not exceeding 0.5 picture elements per picture period the channel having the longest period is used. Thus, to achieve the picture signal bandwidth reduction, use is made of splitting the picture into sub-pictures which are stationary or evidence some motion or much motion, respectively.
The above mentioned system has as drawback a rather costly decoder. It is inter alia an object of the invention to provide a system which allows for a cheaper decoder.